Power transfer device with contactless optical encoder and color reflective surface

ABSTRACT

An angular offset sensing device includes an optical encoder having a light generating element and a light sensor. An armature includes a reflective surface having a generally semicircular shape and a spectrum of color disposed thereon varying from a first end of the surface to a second end of the surface. A housing encloses both the optical encoder and the armature and rotationally supports the armature. An electrical voltage is generated when light from the light generating element is reflected back to the sensor from the reflective surface. The voltage is proportional to a wavelength of the reflected light and is indicative of an angular rotation of the armature relative to the optical encoder. The voltage is corrected for linearity and used for example to signal a vehicle transfer case shift.

FIELD OF THE INVENTION

The present invention relates in general to rotational sensor systemsand more specifically to angular rotational sensor systems used todirect operation of power transfer devices.

BACKGROUND OF THE INVENTION

Systems for determining the position of rotating shafts are known.Existing systems including sensors which determine a relative positionbetween a gear tooth and a reference tooth are known. Other systemsinclude variable reluctance sensors, multiple element tone rings,inductive magnetic sensor systems and systems which utilize one or morebrushes to physically make contact between a rotating part and areference point.

Known systems for determining angular rotation are susceptible to damagefrom environmental conditions such as dirt, grease and oil products.Systems utilizing brushes for contact are additionally susceptible towear and/or oxidation of the brushes which leads to a decreased accuracyof the system as well as increased maintenance costs.

Optical sensors used for determining torque or rotational speed are alsoknown. Optical encoders having two outputs are capable of determiningboth a shaft movement and a direction of shaft movement. Incrementalencoders having a third output are also known which can locate a uniqueangular position on a rotating shaft.

A disadvantage of known systems using optical encoders is that thenumber of light sources such as light emitting diodes (LED) increases asthe complexity of the measurement type increases. This increases thecost of the system and increases the complexity of the circuitryrequired to receive and correlate all of the received signal data. Thereis therefore a need for a system for determining angular rotation whichreduces the number of components required and simplifies the overallcircuitry.

SUMMARY OF THE INVENTION

An angular rotation identification device with a contactless opticalencoder according to a preferred embodiment of the present inventionincludes an optical device having a light generating element and a lightsensor. A reflective surface has a generally semicircular perimetershape and a spectrum of color varying from a first end of the surface toa second end of the surface. An electrical voltage generated by lightfrom the light generating element being reflected back to the sensorupon angular rotation of the reflective surface with respect to theoptical device is proportional to a wavelength of the color.

According to another aspect of the present invention, an angular offsetsensing device includes an optical encoder having a light generatingelement and a light sensor. A reflective surface is integrally includedin an armature. A housing encloses both the optical encoder and thearmature and rotationally supports the armature. An electrical voltagegenerated by light from the light generating element being reflectedback to the sensor from the reflective surface is proportional to awavelength of the light.

According to yet another aspect of the present invention, an opticalangular offset sensing system includes an optical device including alight generating element and a light sensor. A reflective surfaceincludes a generally semicircular perimeter shape and a spectrum ofcolor varying from a first end of the surface to a second end of thesurface. At least one color is disposable on the reflective surfacehaving a wavelength continuously increasing between the first end andthe second end. An electrical voltage controlled by light from the lightgenerating element being reflected back to the sensor from thereflective surface is proportional to the wavelength of the lightreflected to the optical device.

According to yet another aspect of the present invention, a discretecircuit separate from the optical device is operable to convert theelectrical voltage to a linear voltage. The linear voltage is indicativeof a device angular offset.

According to yet another aspect of the present invention, a method forcontrolling a power transfer device using an optical device having alight generating element and a photo-detector device, and a reflectivesurface includes: producing an output light from the light generatingelement; applying a spectrum of color varying from a first end of thereflective surface to a second end of the reflective surface; rotatablypositioning the reflective surface to reflect the light from thereflective surface to the photo-detector device such that a wavelengthof the color continuously increases between the first and second ends;controlling the flow of an electrical current using the photo-detectordevice, the electrical current and voltage being proportional to thewavelength of the color and the electrical current allowed by thephoto-detector; and using the electrical voltage to control a shiftposition of the power transfer device.

According to yet still another aspect of the present invention, a methodfor sensing angular offset using an optical device having a lightgenerating element and a photo-detector device, and a reflective surfaceincludes: producing an output light from the light generating element;applying a spectrum of color varying from a first end of the reflectivesurface to a second end of the reflective surface such that a wavelengthof the color continuously increases between the first and second ends;positioning the reflective surface to reflect the light from thereflective surface to the photo-detector device; and controlling anelectrical voltage using the photo-detector device, the electricalvoltage being proportional to the wavelength of the color.

A power transfer device with contactless optical encoder of the presentinvention provides several advantages. By using an optical encoder toboth transmit light and collect the light after reflection from areflective surface, brushes previously known for the application ofsensing angular rotation are eliminated, which reduces maintenance andimproves sensor life. By varying a range of colors or varying a singlecolor intensity along the reflective surface, a substantially linearvoltage output from the encoder and encoder circuitry is produced whichcan be used to direct the shifting of, for example, a power transfercase. The reflective surface provides a constant slope. A distance fromthe optical encoder to the reflective surface as the reflective surfacerotates therefore changes at a predetermined rate. Rotational motion isthereby sensed as changing reflected light frequency which is convertedto a substantially linear analog signal.

Further areas of applicability of the present invention will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating two preferred embodiments of the invention, are intended forpurposes of illustration only and are not intended to limit the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 is a flow diagram of a power transfer system with contactlessoptical encoder according to a preferred embodiment of the presentinvention;

FIG. 2 is a flow diagram of the optical encoder components for thesystem of FIG. 1;

FIG. 3 is an electrical diagram identifying the components for a sensorof the present invention;

FIG. 4 is an electrical diagram similar to FIG. 3 further identifying anLED output path as well as a reflected light path returning to adetector of the present invention;

FIG. 5 is a plan view of an optical encoder device of the presentinvention;

FIG. 6 is a side elevational view of the optical encoder device of FIG.5;

FIG. 7 is a plan view of a base member of the present invention;

FIG. 8 is a bottom plan view of the base member of FIG. 7;

FIG. 9 is an end elevational view of the base member of FIG. 7;

FIG. 10 is a plan view of a circuit board of the present invention;

FIG. 11 is a side elevational view of the circuit board of FIG. 10;

FIG. 12 is a perspective view of an armature of the present invention;

FIG. 13 is a plan view of the armature of FIG. 12 providing a reflectivesurface for the optical encoder of the present invention;

FIG. 14 is a cross sectional view taken at section 14 of FIG. 13;

FIG. 15 is a plan view of a cover element for the optical encoder of thepresent invention; and

FIG. 16 is a side elevational view of the cover element of FIG. 15.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiments is merelyexemplary in nature and is in no way intended to limit the invention,its application, or uses.

Referring generally to FIG. 1 and according to a preferred embodiment ofthe present invention, an optical encoding system 10 includes an opticalencoder 12 connectible to a gear train 14. The gear train 14 issubsequently connected to an electric motor 16. Optical encoder 12 isalso connected to an electronic control module (ECM) 18 to feedelectrical output signals from optical encoder 12 to ECM 18 via acommunication path 20. Optical encoder 12 is connected to a shaft 21 ofgear train 14 such that angular rotation of shaft 21 can be determinedby optical encoder 12. Electrical signals from optical encoder 12 sentto ECM 18 are used to control the rotational speed of motor 16. Geartrain 14 is used to convert the relatively high rotational speed and lowtorque of motor 16 to a relatively lower speed, high torque output. Geartrain 14 is also used to control the shift position of a movableactuation device 19 associated with the power transfer device 22 whichin one embodiment of the present invention includes a transfer case foran automobile vehicle (not shown). Such actuation devices 19 mayinclude, without limitation, a range shift mechanism of a multi-speedgearset or a clutch actuator used to apply a clutch engagement force ona friction clutch.

Referring generally to FIG. 2, optical encoder 12 includes a sensor 23positioned adjacent to an armature 24. Light generated by sensor 23 istransmitted to armature 24 as input light 26. Light reflected byarmature 24 is returned to sensor 23 as reflected output 28. A discreetexternal circuit 30 is connected to sensor 23 via a circuit input line32 and a circuit output line 34. A microcontroller 36 is also connectedto sensor 23 via an input line 38 and an output line 40, respectively.Electrical signals generated by microcontroller 36 are forwarded to ECM18 as output electrical signals 42 via a microcontroller output line 44.Electrical power for sensor 23 is provided from ECM 18 to sensor 23 viaa sensor input voltage line 46.

Referring next to FIG. 3, individual components of sensor 23 include ananode 47 which connects electrical voltage to a light emitting diode(LED) 48. Current from anode 47 flows through LED 48 and is dischargedvia a cathode 50 to ground. Sensor 23 further includes a collector 52which also receives a current input to supply a photo-transistordetector 54. Current from collector 52 transferred via photo-transistordetector 54 is discharged via an emitter 56.

Referring now specifically to FIG. 4, the operation of sensor 23 isfurther identified. Current from anode 47 to LED 48 generates a lightoutput which is transmitted via a light transparent surface 58 to areflective surface 60 of armature 24. The input light 26 is reflected byreflective surface 60 and returned as reflected output 28 tophoto-transistor detector 54. As reflected output 28 reachesphoto-transistor detector 54, the voltage across photo-transistordetector 54 increases in proportion to the amount and frequency ofreflected light received. A separation distance “A” is normally providedbetween light transparent surface 58 of sensor 23 and reflective surface60. In one preferred embodiment of the present invention separationdistance “A” is approximately 1.5 millimeters.

Referring generally to FIGS. 5 and 6, optical encoder 12 according toone preferred embodiment of the present invention is constructed witharmature 24 having reflective surface 60 enclosed between a base member62 and a cover member 64, respectively. Base member 62 and cover member64 can be provided of a polymeric material which is preferably molded tothe shapes identified in FIGS. 5 and 6. A circuit board 66 is disposedbetween base member 62 and cover member 64. Circuit board 66functionally supports sensor 23. Sensor 23 is connected to circuit board66 by known techniques such as using conductive adhesive or bysoldering. Sensor 23 is thereby fixedly connected to circuit board 66.Armature 24 is rotatably received between cover member 64 and circuitboard 66 such that armature 24 can be coupled to shaft 21 (shown in FIG.1). Base member 62 is connected to cover member 64 via a perimeter wall68 of base member 62 being slidably received within an annular slot 70of cover member 64. Separation distance “A” is clearly distinguishablein reference to FIG. 6. An assembly width “B” of base member 62 andcover member 64 is approximately 11.2 mm in one preferred embodiment ofthe present invention. A plurality of electrical leads 72 are connectedto circuit board 66 and in the embodiment shown in FIG. 5 extend outwardfrom optical encoder 12 for connection to external electricalconnections. Electrical connections made to leads 72 include a voltagesupply such as sensor input voltage line 46 as well as groundconnections and sensor 23 voltage/current output connections.

Referring generally now to FIGS. 7 through 9, base member 62 furtherincludes a through aperture 74 with a through aperture diameter “E”provided through a sleeve 75 having a sleeve outer diameter “F”. Anopposed pair of engagement wall surfaces 76 have a wall spacing “G”defining a cavity 78 there-between. Cavity 78 has a cavity width “H”.Annular slot 70 is provided between perimeter wall 68 and an innerperimeter wall 77. Perimeter wall 68 has an outer diameter “J”. Annularslot 70 is defined between a base perimeter wall inner diameter “K” andan inner wall outer diameter “L” of inner perimeter wall 77.

In one preferred embodiment of the present invention, through aperturediameter “E” is approximately 22.3 millimeters, sleeve outer diameter“F” is approximately 25.3 millimeters, wall spacing “G” is approximately25.1 millimeters and cavity width “H” is approximately 22.6 millimeters.It is further noted that in one preferred embodiment of the presentinvention, base outer diameter “J” is approximately 58.65 millimeters,base perimeter wall inner diameter “K” is approximately 56.15millimeters and inner wall outer diameter “L” is approximately 53.5millimeters. Through aperture diameter “E” provides clearance forslidably mounting armature 24 to sleeve 75. These dimensions areexemplary of one preferred embodiment of the present invention. Itshould be obvious that the dimensions provided herein can be varied forany application of an optical encoding system 10 of the presentinvention.

Referring generally now to both FIGS. 10 and 11, circuit board 66includes a perimeter 79 having a diameter “M”. A circuit board aperture80 is also provided having an aperture diameter “N”. Sensor 23 isdirectly connectible to a surface 82 of circuit board 66 by forming aconnecting joint 84. As previously noted, connecting joint 84 can bemade using a conductive adhesive, a solder joint or other knownelectrical contact joining techniques. FIG. 11 also identifies that asubstantial portion of leads 72 extend outwardly beyond perimeter 79 ofcircuit board 66. Leads 72 are also connected to surface 82 similar tosensor 23.

In one preferred embodiment of the present invention, diameter “M” isapproximately 53 millimeters such that circuit board 66 is capturedwithin base perimeter wall inner diameter “K” and physically retainedagainst inner perimeter wall 77 as shown in FIG. 5. Circuit board 66further includes a circuit board thickness “P”. According to onepreferred embodiment of the present invention, circuit board thickness“P” is approximately 1.1 millimeters.

Referring now to FIG. 12, armature 24 includes reflective surface 60formed on a first side of a semispherical flange portion 86. A reduceddiameter flange portion 88 is oppositely positioned from semisphericalflange portion 86. An engagement tooth 90 is provided within a sleeve 92which longitudinally extends through armature 24 and is coaxiallyaligned with an armature axis of rotation 94. Shaft 21 (shown inreference to FIG. 1), is slidably received within sleeve 92. A suitablereceiving slot (not shown) is formed within shaft 21 which receivesengagement tooth 90. Any rotation of shaft 21 therefore provides anequivalent rotation of armature 24.

Referring generally now to both FIGS. 13 and 14, sleeve 92 provides asleeve inner wall 96 to slidably receive shaft 21. At least one color 97is disposed as a spectrum of color or as a color scale on reflectivesurface 60. In the embodiment shown, color 97 starts at a first end 98of semispherical flange portion 86 and extends to a second end 100 ofsemispherical flange portion 86. Color 97 can be provided as shownranging from a violet to a red color spectrum. In another embodiment ofthe present invention (not shown) color 97 is formed as varyingintensities of a color such as black beginning at first end 98 as alight black or gray and extending to a fully black color adjacent-secondend 100. Semispherical flange portion 86 is defined within an angle E.Angle θ can vary at the discretion of the designer and to suit a desiredangular rotation of shaft 21. In one preferred embodiment of the presentinvention, angle θ is approximately 180°. In an alternate embodiment ofthe present invention angle θ is approximately 155°.

Semispherical flange portion 86 includes a semishere radius “Q”. Reduceddiameter flange portion 88 includes a radius “R”. In one preferredembodiment of the present invention, semisphere radius “Q” isapproximately 22.28 millimeters and radius “R” is approximately 15.2millimeters.

Referring now to FIGS. 4, 5 and 13, light from sensor 23 is emitted byLED 48, reflected from reflective surface 60 and received byphoto-transistor detector 54. The light reflected from reflectivesurface 60 has a wavelength which is determined by the particular coloror intensity of color disposed along reflective surface 60. Anelectrical voltage produced by photo-transistor detector 54 is thereforedirectly proportional to a wavelength of the reflected light. Opticalencoding system 10 therefore provides an electrical signal from opticalencoder 12 which is directly proportional to the wavelength of reflectedlight. As armature 24 rotates with respect to sensor 23, the outputvoltage of sensor 23 varies with the wavelength of the reflected light.This permits a direct correlation between the output voltage of sensor23 and an angular rotation of shaft 21. Because armature 24 and circuitboard 66 are substantially enclosed between base member 62 and covermember 64, contaminants are prevented from contacting reflective surfaceor sensor 23. This reduces the chance that reflected light fromreflective surface 60 will vary in wavelength based on surfacecontamination.

Referring next to both FIGS. 15 and 16, cover member 64 includes aperimeter wall 102 which when assembled with base member 62 as seen inFIG. 6, extends outwardly of perimeter wall 68. Cover member 64 alsoincludes an aperture 104 having an aperture diameter “U”. An opposedpair of engagement surfaces 106 are created at one location of perimeterwall 102. A clearance dimension “V” is provided between engagementsurfaces 106. In one preferred embodiment of the present invention,cover diameter “S” is approximately 55.6 millimeters, cover innerdiameter “T” is approximately 53.6 millimeters, aperture diameter “U” isapproximately 20.8 millimeters and clearance dimension “V” isapproximately 18.3 millimeters.

As armature 24 rotates relative to circuit board 66 and sensor 23,sensor 23 receives reflected light in wavelengths in the visible lightregion of the electromagnetic spectrum between approximately 35nanometers to approximately 1,000 nanometers. In one preferredembodiment of the present invention, the received wavelengths rangebetween approximately 35 nanometers to approximately 750 nanometers andcorrespond to an angle θ of approximately 155°. A voltage produced bysensor 23 ranges from zero to approximately 5 volts DC. A linear outputvoltage of sensor 23 is desirable to provide quantifiable ranges ofvoltages corresponding to desired shift points of power transfer device22. Both external circuit 30 and microcontroller 36 are thereforeprovided to convert the output voltage of sensor 23 to a linear outputvoltage.

Referring back to FIGS. 1 through 4, sensor 23 receives input voltagefrom ECM 18 which is distributed to both anode 47 and collector 52.Light generated by LED 48 is directed towards reflective surface 60. Thecolor or spectrum of colors provided on reflective surface 60 reflectslight back to sensor 23 at a wavelength of the color at the relativeposition on reflective surface 60 directly adjacent to sensor 23. Thereceived light is converted to an electrical voltage having a range ofapproximately 0 to 5 volts DC by photo-transistor detector 54 andemitted by emitter 56. This voltage is corrected by external circuit 30and/or microcontroller 36 to a linear output voltage. The linear outputvoltage is forwarded by microcontroller 36 to ECM 18 where the voltagesignal is used to direct motor 16 and gear train 14 to reposition powertransfer device 22.

ECM 18 receives an operator's command for shifting power transfer device22 to a desired position. ECM 18 generates a pulse width modulationsignal which supplies power to motor 16 and gear train 14 to move powertransfer device 22 to an appropriate position. Rotational movement ofmotor 16 and gear train 14 determines an angular position of opticalencoder 12. The output of motor 16 is used as the input to gear train 14to convert the relatively high speed, low torque output of motor 16 tothe relatively low speed, high torque ouput from gear train 14. The lowspeed, high torque output of gear train 14 is used to shift theactuation devices 19 within power transfer device 22 and also to definea position of motor 16 via optical encoder 12. Typical shift positionsassociated with a power transfer device 22 having a two-speed gearreduction unit and an adaptive transfer clutch include 4 HI, AWD, 2 HI,neutral, and 4 LO. These positions are representative of an all-wheeldrive vehicle. Similar positions can also be obtained for a powertransfer device of a two-wheel drive and/or a four-wheel drive vehicle.

A power transfer device with contactless optical encoder of the presentinvention provides several advantages. By using an optical encoder toboth transmit light and collect the light after reflection from areflective surface, brushes previously known for this application ofsensing angular rotation are eliminated. This reduces maintenance andimproves system operational life. By varying a range of colors orvarying a single color intensity along the reflective surface, asubstantially linear voltage output from the encoder and encodercircuitry is used to direct the shifting of, for example, a powertransfer case. The reflective surface is created on an armature. Adistance from the optical encoder to the reflective surface as thereflective surface rotates is maintained at a substantially constantvalue. Rotational motion is thereby sensed as a changing reflected lightfrequency which is converted to a substantially linear analog signalwithout the need for physical contact between the sensor and armature.

The description of the invention is merely exemplary in nature and,thus, variations that do not depart from the gist of the invention areintended to be within the scope of the invention. Such variations arenot to be regarded as a departure from the spirit and scope of theinvention.

1. An angular rotation identification device, comprising: an opticaldevice including a light generating element and a light sensor; and areflective surface having a generally semicircular perimeter shape and aspectrum of color varying from a first end of the surface to a secondend of the surface; wherein an electrical voltage generated by lightfrom the light generating element being reflected back to the sensorupon angular rotation of the reflective surface with respect to theoptical device is proportional to a wavelength of the color.
 2. Thedevice of claim 1, further comprising a printed circuit board operableto support the optical encoder.
 3. The device of claim 2, furthercomprising: an armature integrally including the reflective surface; anda housing operable to rotatably support the armature and fixedly supportthe printed circuit board.
 4. The device of claim 3, wherein the housingfurther comprises: a base having a sleeve operable to support thearmature; and a cover connectable to the base, the base and covertogether operable to enclose both the armature and the printed circuitboard.
 5. The device of claim 1, wherein the voltage comprises a voltagerange variable between approximately 0 volts DC to approximately 5 voltsDC.
 6. The device of claim 5, wherein the spectrum of color furthercomprises: a first color wavelength at the first end corresponding tothe 0 volts DC voltage; and a second color wavelength at the second endcorresponding to the 5 volts DC voltage.
 7. The device of claim 5,wherein the voltage generated by the optical device at any locationbetween the first and second ends is proportional to a relative positionof the optical device between the first and second ends.
 8. The deviceof claim 1, wherein the light generating element further comprises alight emitting diode.
 9. The device of claim 1, wherein the light sensorfurther comprises a detector having a collector and an emitter.
 10. Thedevice of claim 1, wherein the first end and the second end are spaced apredetermined number of degrees apart from each other.
 11. An opticalangular offset sensing device, comprising: an optical encoder includinga light generating element and a light sensor; an armature including areflective surface, the reflective surface having a generallysemicircular shape and a spectrum of color disposed thereon varying froma first end of the surface to a second end of the surface; and a housingoperable to enclose both the optical encoder and the armature androtationally support the armature; wherein an electrical voltagegenerated by light from the light generating element being reflectedback to the sensor from the reflective surface is proportional to awavelength of the light reflected from the reflective surface to theoptical encoder and is indicative of an angular rotation of the armaturerelative to the optical encoder.
 12. The device of claim 11, wherein thefirst and second ends are spaced a predetermined number of degrees apartfrom each other.
 13. The device of claim 11, wherein the reflectivesurface comprises a variable reflectivity surface.
 14. The device ofclaim 13, wherein the variable reflectivity surface comprises aplurality of colors having an increasing range of wavelengths betweenthe first and second ends.
 15. An optical angular offset sensing system,the system comprising: an optical device including a light generatingelement and a light sensor; a reflective surface having a generallysemicircular perimeter shape and a spectrum of color varying from afirst end of the surface to a second end of the surface; and at leastone color disposable on the reflective surface having a wavelengthcontinuously increasing between the first end and the second end;wherein an electrical voltage generated by light from the lightgenerating element being reflected back to the sensor from thereflective surface is proportional to the wavelength of the lightreflected to the optical device.
 16. The system of claim 15, wherein thewavelength of the light further comprises a continuously increasingwavelength between the first end and the second end.
 17. The system ofclaim 15, wherein the at least one color comprises a plurality of colorsspectrally ranging from violet to red.
 18. The system of claim 15,wherein the at least one color comprises a single color having acontinuously increasing color intensity along the reflective surfacebetween the first end and the second end.
 19. An optical angular offsetsensing system, the system comprising: an optical device including alight generating element and a light sensor; a reflective surface havinga generally semicircular perimeter shape and a spectrum of color varyingfrom a first end of the surface to a second end of the surface; at leastone color disposable on the reflective surface such that a wavelength ofthe color continuously increases between the first and second ends; anelectrical voltage generated by light from the light generating elementbeing received by the sensor after reflection from the reflectivesurface; and a discrete circuit separate from the optical deviceoperable to convert the electrical voltage to a linear voltageindicative of a device angular offset.
 20. The system of claim 19,further comprising a circuit board operable to fixedly support theoptical device.
 21. The system of claim 20, further comprising a baseoperable to support the circuit board.
 22. The system of claim 21,further comprising a cover connectable to the base and operable togetherwith the base to enclose the circuit board.
 23. An optical angularoffset sensing system, the system comprising: an optical deviceincluding a light generating element and a light sensor; a reflectivesurface having a generally semicircular perimeter shape and a spectrumof color varying from a first end of the surface to a second end of thesurface such that an electrical voltage is generated by light from thelight generating element being received by the sensor after reflectionfrom the reflective surface; at least one color disposable on thereflective surface wherein a wavelength of the color continuouslyincreases between the first and second ends; and an electronic controlmodule connected to the optical device, the electronic module operableto receive the electrical voltage generated by the sensor and utilizethe electrical voltage to control a shift position of an automotivetransfer case.
 24. The system of claim 23, further comprising a discretecircuit separate from the optical device operable to change theelectrical voltage to a linear voltage.
 25. The system of claim 23,further comprising an electrical motor connected between the electroniccontrol module and the transfer case.
 26. The system of claim 25,further comprising a gear train connected between the motor and thetransfer case, the gear train operable to change the shift position ofthe transfer case.
 27. The system of claim 26, wherein the gear trainfurther comprises an output shaft, wherein the electrical voltage isdirectly proportional to an angular position of the output shaft. 28.The system of claim 23, further comprising a microcontroller connectedbetween the electronic control module and the optical device.
 29. Amethod for controlling a power transfer device using an optical devicehaving a light generating element and a photo-detector device, and areflective surface, the method comprising: producing an output lightfrom the light generating element; applying a spectrum of color varyingfrom a first end of the reflective surface to a second end of thereflective surface; rotatably positioning the reflective surface toreflect the light from the reflective surface to the photo-detectordevice such that a wavelength of the color continuously increasesbetween the first and second ends; generating an electrical voltageusing the photo-detector device, the electrical voltage beingproportional to the wavelength of the color; and utilizing theelectrical voltage to control a shift position of the power transferdevice.
 30. The method of claim 29, further comprising connecting anelectronic control module to the optical device.
 31. The method of claim30, further comprising connecting a discrete circuit to the opticaldevice.
 32. The method of claim 31, further comprising changing theelectrical voltage to a linear voltage using the discrete circuit. 33.The method of claim 29, further comprising applying a plurality ofcolors having an increasing range of wavelengths to the reflectivesurface between the first and second ends.
 34. A method for sensingangular offset using an optical device having a light generating elementand a photo-detector device, and a reflective surface, the methodcomprising: producing an output light from the light generating element;applying a spectrum of color varying from a first end of the reflectivesurface to a second end of the reflective surface such that a wavelengthof the color continuously increases between the first and second ends;positioning the reflective surface to reflect the light from thereflective surface to the photo-detector device; and generating anelectrical voltage using the photo-detector device, the electricalvoltage being proportional to the wavelength of the color.
 35. Themethod of claim 34, further comprising fixedly connecting the opticaldevice to a circuit board.
 36. The method of claim 35, furthercomprising fixedly mounting the circuit board to a base member.
 37. Themethod of claim 36, further comprising co-molding the reflective surfaceto an armature.
 38. The method of claim 37, further comprising rotatablymounting the armature to the base member.
 39. The method of claim 36,further comprising attaching a cover to the base member, the cover andthe base member together operable to enclose the circuit board.
 40. Themethod of claim 37, further comprising rotating the armature within anangular range of approximately 155 degrees.